Form-rolling machine



Jan. 10, 1967 D. H. PRUTTON FORMROLLING MACHINE 2 Sheets-Sheet 1 Filed April 8, 1964 INVENTOR DANIEL H. PRUTTON ATTORNEY Jan. 10, 1967 Filed April 8, 1964 D. H. PRUTTON FORM'ROLLING MACHINE 2 Sheets-Sheet 2 INVENTOR.

DANIEL H. PRUTTON BY a /N ATTORN EY United States Patent 3,286,845 FGRM-RQYLLING MAQIHINE Daniel H. Frutton, 5385 W. 138th St Cleveland, @hio 441% Filed Apr. 8, 1964, Ser. No. 358,161 16 Uaims. (Cl. 72--10tl) The invention relates in general to machines for rolling non-cylindrical forms on a workpiece and more particularly to a machine for rolling threads on workpieces.

The machine may be used for rolling threads, spiral gears or splines on a workpiece or any rolled form other than cylindrical.

Thread-rolling machines have been used wherein thread-rolling dies have cooperated with a workpiece to roll a thread into the workpiece. In many cases these dies are moved in a path with a radial component to control the depth of thread-rolling. The means to move the dies has, in many cases, been of insufiicient strength to withstand the considerable pressures developed during high speed thread-rolling with consequent flow and displacement of material during the cold forming of the threads. As a result, imperfectly formed workpieces have resulted, as well as workpieces with surface finishes which have been less that satisfactory, requiring slower operation of the machine for satisfactory workpieces. In the case of rolling the ordinary V-shaped thread, if the material is moved or displaced too rapidly, cold shuts may result at the crest of the thread, where the flow of metal rolls over from each side surface at the crest rather than smoothly flowing into a sharp V at the crest.

Accordingly, an object of the invention is to provide a machine overcoming the above disadvantages.

Another object of the invention is to provide a machine to roll noncylindrical workpieces wherein the surfaces are worked from opposite directions during a cycle of operation.

Another object of the invention is to provide a threadrolling machine wherein the thread surfaces are worked first in one direction and then in another to perform a finishing operation resulting in a thread of superior smooth surface.

Another object of the invention is to provide a thread rolling machine which is rugged and dependable and which will not distort out of position due to the high thread-rolling pressures, thus resulting in a superior workpiece.

Another object of the invention is to provide control means for the relative timing of one thread-rolling die relative to another during a cycle of operation to perform a finishing operation on one side of the thread of the workpiece.

Other objects and a fuller understanding of this invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a plan view of a machine embodying the invention;

FIGURE 2 is a sectional elevational view on line 22 of FIGURE 1;

FIGURE 3 is an enlarged diagrammatic developed View of the thread-rolling die surfaces; and

FIGURE 4 is an enlarged sectional view of a threaded workpiece.

FIGURES 1 and 2 show a machine 11 embodying the invention and this machine has been shown as a threadrolling machine, merely as an illustration of one form of the invention. The machine 11 has a frame 12 including an upper casting 13, a table 14 on the top thereof and a lower housing 15. A plurality of die holders 1'7 are journalled in the upper casting 13 on vertical axes.

Three such die-holders have been illustrated and all are identical with FIGURE 2 showing one of these die-holders in section. Each die-holder 17 is a large cylindrical shaft journalled in a large bearing surface 18 in the upper casting 13. Each die-holder is held in vertical position by a circular key 19 fastened in the casting 13 by machine screws, not shown. This circular key 19 permits partial rotational movement of the die-holder 17 without vertical movement. The three die-holders 17 are journalled on axes parallel to a main axis 20 which is a central axis of the machine 11.

A main shaft 22 is journalled in the lower housing 15 on the main axis 20. A worm gear 23 is fixed on the main shaft 22. A worm wheel 24 meshes with the worm gear 23 and is driven from a motor 25. A main spiral gear 26 is fixed on the main shaft 22 for rotation therewith.

Each die-holder 17 has a drive shaft 28 journalled therein on the axis of the respective die-holder. The lower end of this drive shaft is externally splined at 29. These splines mate with female splines 30 on a driven spiral gear 31. Each of these driven spiral gears mesh with the main spiral gear 26 and are uniformly spaced around the periphery thereof. The driven spiral gear 31 is carried in thrust and radial bearings 32 in a sleeve 33. A lock nut 34 secures the driven spiral gear 31 within the sleeve 33 to eliminate relative longitudinal movement therebetween.

A die shaft 37 is eccentrically journalled in each dieholder 17 by bearings 38. The bearings 38 are radial and thrust bearings and are widely spaced to provide ample bearing surface to resist the high rolling pressures. Each die shaft 37 carries a gear 39 meshing with a gear 40 on the respective drive shaft 28 for rotation of said die shaft with said drive shaft. The upper end of each die shaft 37 is splined at 41 to rotationally drive a die 42. These dies have external forms suitable to form-roll the desired contour on the workpiece. In this case a form for rolling a thread is shown. These three thread-rolling dies 42 are on axes parallel to the main axis 20 and spaced uniformly around this axis. The three threadrolling dies cooperate with a workpiece blank 44. This workpiece 44 has been shown as a machine screw merely for purposes of illustration. This workpiece may be supported on a pedestal 45 threaded into the upper casting 13 along the main axis 20. The height of such pedestal 45 may readily be changed to accommodate different lengths of workpieces.

A gear sector 48 is cut into or otherwise fastened to the upper end of each die-holder and meshes with an internal ring gear 49. This ring gear is carried on the table 14 for partial rotation. A radial depth cam 50 is journalled on a vertical axis on the table 14 and cooperates with a cam follower 51. This cam follower is carried on a slide 52 connected by a pivot pin 53 to the ring gear 49. A spring 54 may also be employed to aid return of the ring gear 49 to an initial position. The radial depth cam 58 may have a generally spiral cam surface therein for a first arc, for example 270, to control gradual clockwise movement of each dieholder 17. This will gradually move the thread-rolling dies 42 in a direction having a radially inward component to feed the dies inwardly to establish a thread of full depth on the workpiece 44 during a thread-rolling cycle of operation. The remaining second are on the radial depth cam 50 which may be in the order of for example, will retract the die-holders in a counter-clockwise direction to release the finished workpiece 44 so that it may be removed and a new blank inserted. Feeding means for feeding and removing the workpieces has not been shown but any conventional feed means may be used.

Accordingly, one revolution of the radial depth cam controls one cycle of operation of thread-rolling on the workpiece 44.

An adjusting block 56 is fixed to one of the sleeves 33. This adjusting block may slide vertically in a slot 57 in the side of the lower housing 15. A slide block 58 may be dove-tailed to the adjusting block 56 and be fixed thereto by a screw 59. The slide block 58 carries a cam follower 60 cooperating with control means shown as a control cam 61. This control cam 61 is a face cam driven by gearing 62 from the motor 25 and this gearing 62 includes change gears 63 and 64 which may readily be changed to change the speed reduction ratio. Gearing 65 is also provided from the motor 25 to the radial face cam 50.

Preferably, there is a control cam 61 for each of two of the sleeves 33 and the respective thread-rolling dies 42. However, only one such sleeve 33 may be provided with a control cam 61 or, alternatively, all three sleeves 33 may be so provided. Rotation of the control cam 61 moves the cam follower 60 in a vertical path which, accordingly, moves the adjusting block 56 and sleeve 33 vertically. This longitudinally moves the driven spiral gear 31 relative to the main spiral gear 26 while remaining in mesh therewith. Accordingly, this changes the rotational position of such driven spiral gear relative to the main spiral gear 26 and, assuming that this main spiral gear is being rotationally driven at a constant speed, the rotational speed of the driven spiral gear 31 will change slightly during this longitudinal movement. The rotational speed of the respective thread-rolling dies 42 will also be changed accordingly-to change the effective timing thereof. The adjusting screw 59 may be used to provide initial adjustment of the longitudinal position of the sleeve 33 so that the three thread-rolling dies 42 may be initially synchronized at the start or at least at the end of the thread-rolling operation. Each thread-rolling die 42 has a thread forming contour which, as shown in FIGURE 3, is a thread. This usually is a multiple start thread because the diameter of the dies 42 is greater than the diameter of the workpiece 44. In FIGURE 3 the three thread-rolling dies 42 have been illustrated in developed view and the workpiece 44 has been diagrammatically illustrated as cooperating with each of the three dies 42A, 42B and 42C. The workpiece 44 is shown as cooperating with the die 42A at the start of the threads thereon. It cooperates with the die 42B along a line displaced 120 from the start of the threads thereon and cooperates with the die 420 along a line displaced 240 in phase from the start of the threads thereon.

Operation In operation, the motor 25 provides power for all functions in rotating the main spiral gear 26, the radial depth cam 50 and the one or more control earns 61. One revolution of the radial depth cam 50 clockwise from the position shown will, for about the first 270, move the die-holders 17 clockwise, thus providing eccentric movement to the thread-rolling dies 42. This has a radially inward component to feed the dies 42 inwardly to the proper depth on the workpiece 44. During the remaining about 90 of arcuate movement of the radial depth cam 50, the dies 42 will be retracted from the workpiece 44 so that it may be removed and another workpiece blank inserted for the next cycle of operation.

At the beginning of thread-rolling on a particular workpiece 44, the adjusting screws 59 have been adjusted to synchronize the start of the threads on the dies 42. This is the proper position for synchronized thread-rolling of all three dies42. The control cam 61 may have a spiral similar to that shown on the cam 50 to gradually move the driven spiral gear 31 in a first longitudinal direction. This will gradually rotate the respective die 42, and in FIGURE 3 this might be die 42B in a first arcuate direction 68. This die 42B may be moved to the phantom line position shown in FIGURE 3 which effectively changes the timing of the threads on the die 42B relative to the timing of the die 42A. At the same time, the respective control cam 61 for the die 42C may arcuately move this die 42C in the opposite arcuate direction 69. Near the end of one cycle of operation the control earns 61 move the driven spiral gears back to the synchronized position shown in full lines in FIGURE 3. Considering just the action of the die 42B on the workpiece 44 partially shown in FIGURE 4, the movement in the first arcuate direction 68 effectively moves the thread form on the die upwardly as shown by arrow 70 to perform a finishing operation on the lower spiral surface forming the thread on the workpiece. At the same time, the oppositely moving die 420 will provide a downward force as shown by arrow 71 on the upper spiral surface of the V forming the thread on the workpiece 44. Preferably, the die 42A is not moved from its synchronous position and, thus, this die 42A aids in holding the workpiece 44 in its preferred longitudinal position in engagement with the pedestal 45. Further, the oppositely acting forces on the workpiece 44 from the dies 42B and 42C counteract any tendency toward longitudinal movement of the workpiece 44. This longitudinally upward movement 70 has been found to more effectively displace the metal and cause it to flow from the cylindrical surface on the blank to the threaded surface on the finished workpiece in a smoother and more facile manner. This controlled flow of metal has been found to eliminate the cold shuts which many times occur in rolling of threads, especially at the crest of the V-shaped threads. Normally, metal being displaced from the space at the root of the thread to form the crest of the thread may roll over and form a slight V depression at the crest. This V depression, once it starts to form, rapidly becomes aggravated and becomes a cold shut when the metal forms around it. It has been found that this finishing operation on alternate sides of the spiral surface forming the threads produces a smoother surface of thread, eliminates cold shuts and permits faster threadrolling.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. A form-rolling machine comprising in combination, a frame having an axis, a plurality of form-rolling dies journalled relative to said frame generally parallel to a main axis and equally spaced therearound for cooperation with a workpiece positionable on said axis, means to relatively rotate any said workpiece and said dies for rolling a form on said workpiece, radial depth means to control radial movement of said form-rolling dies to control radial depth of form-rolling on any workpiece coaxial with said axis, a means to adjust the relative timing of the form-rolling means on the respective dies to be synchronized at the end of each cycle of operation, and control means connected to move one of said dies to change the effective timing thereof relative to the others first in one direction and then return in the opposite direction to said synchronized position to perform a finishing operation on the form rolled on the workpiece during the thread-rolling operation.

2. A form-rolling machine comprising in combination, a frame having an axis, a plurality of form-rolling dies journalled relative to said frame generally parallel to said axis and equally spaced therearound for cooperation with a workpiece positionable on said axis, means to relatively rotate any said workpiece and said dies for rolling a form on said workpiece, a means to adjust the relative timing of the form-rolling means on the respective dies to be synchronized at the end of each cycle of operation, and control means connected to move one of said dies to change the effective timing thereof relative to the others first in one direction and then return in the opposite direction to said synchronized position to perform a finishing operation on the form rolled on the workpiece during one cycle of operation.

3. A form-rolling machine comprising in combination, a frame, a plurality of form-rolling dies journalled relative to said frame generally parallel to a main axis and equally spaced therearound, means to drive each said die including a main gear journalled on said frame and a driven gear meshed therewith and movable relative thereto in a path While remaining in mesh to change the effective timing of one of said dies at least during rotation of said main gear, radial depth means to control radial movement of said form-rolling dies to control radial depth of formrolling on any workpiece coaxial with said axis, control means connected to move said driven gear in said path to change the effective timing of said one of said dies relative to the others, means to adjust the relative timing of the form-rolling means on the respective dies to be synchronized at the end of each cycle of operation, and said control means moving said driven gear on said path to change the timing of the respective form-rolling die relative to the others first in one direction from synchronized position and then return in the opposite direction to said synchronized position to perform a finishing operation on the form rolled on the workpiece during one cycle of operation.

4. A thread-rolling machine comprising in combination, a frame, a plurality of dies having a form for rolling a thread and journalled relative to said frame generally parallel to a main axis and equally spaced therearound, means to drive each said die including a main gear journalled on said frame and a driven gear meshed therewith and movable relative thereto in a path while remaining in mesh to change the effective timing of one of said dies at least during rotation of said main gear, radial depth means to control radial movement of said thread-rolling dies to control radial depth of thread-rolling on any workpiece coaxial with said axis, a control cam journalled relative to said frame, a cam follower cooperating with said control cam, means connecting said cam follower to move said driven gear in said path to change the effective timing of said one of said dies relative to the others, means to adjust the relative timing of the thread-rolling means on the respective dies to be synchronized at the beginning of each cycle of operation, and rotation of said control cam moving said driven gear on said path to change the timing of the respective thread-rolling die relative to the others first in one direction from synchronized position and then return in the opposite direction to said synchronized position to perform a finishing operation on one side of the thread formed during the thread rolling operation.

5. A form-rolling machine comprising in combination, a frame, a plurality of form-rolling dies journalled relative to said frame generally parallel to a main axis and equally spaced therearound, means to drive each said die including a main gear journalled on said frame and a driven gear meshed therewith and movable relative thereto in a path while remaining in mesh to change the rotational speed of said driven gear at least during rotation of said main gear, radial depth means to control radial movement of said form-rolling dies to control radial depth of formrolling on any workpiece coaxial with said axis, a control cam journalled relative to said frame, a cam follower cooperating with said control cam, means connecting said cam follower to move said driven gear in said path to change the rotational speed of the respective one (if said form-rolling dies relative to the others, means to adjust the relative timing of the form-rolling means on the respective dies to be synchronized at the beginning of each cycle of operation, and rotation of said control cam moving said driven gear on said path to change the timing of the respectiveform-rolling die relative to the others first in one arcuate direction from synchronized position and then return in the opposite arcuate direction to said synchronized position to perform a finishing operation on the form rolled on the workpiece.

6. A thread-rolling machine comprising in combination, a frame, a plurality of thread-rolling dies journalled relative to said frame generally parallel to a main axis and equally spaced therearound, means to drive each said die at the same rotational speed, including a main spiral gear jtiurnalled on said frame, a driven spiral gear longitudinally movable relative to said main spiral gear and meshing therewith, means connecting said driven spiral gear to rotate one of said dies, radial depth means to control radial movement of said thread-rolling dies to control radial depth of thread-rolling on any workpiece coaxial with said axis, a control cam journalled relative to said frame, a cam follower cooperating with said control cam, means connecting said cam follower to longitudinally move said driven spiral gear to partially rotate the respective one of said thread-rolling dies relative to the others, means to adjust the relative timing of the thread-rolling means on the respective dies to be synchronized at the beginning of each cycle of operation, and rotation of said control cam longitudinally moving said driven spiral gear to change the timing of the respective thread-rolling die relative to the others first in one arcuate direction from synchronized position and then return in the opposite arcuate direction to said synchronized position to perform a finishing operation on one side of the thread formed during the thread-rolling operation.

7. A thread-rolling machine comprising in combination, a frame, a plurality of die holders journalled relative to said frame parallel to a main axis and equally spaced therearound, a die shaft eccentrically journalled on each said die holder on an axis generally parallel to said main axis, a thread-rolling die with a thread formed thereon fixed on each die shaft for cooperation with a workpiece coaxial with said main axis, said thread-rolling dies being symmetrically spaced around the periphery of said workpiece, means to drive each said die shaft at the same rotational speed including a main spiral gear journalled on said frame, a driven spiral gear longitudinally movable relative to said main spiral gear and meshing therewith, means connecting said driven spiral gear to rotate one of said dies, radial depth means to control partial rotation of said die holders to control eccentric movement of said threadrolling dies to control radial depth of thread-rolling on said workpiece, a control cam journalled on said frame, a cam follower cooperating with said control cam, means connecting said cam follower to longitudinally move said driven spiral gear to partially rotate the respective one of said thread-rolling dies relative to the others, and revolution of said control cam during thread rolling changing the timing of the start of the thread of the respective thread-rolling die relative to the others to perform a finishing operation on one side of the thread formed during thread rolling.

8. A thread-rolling machine comprising in combination, a frame, a plurality of die holders journalled relative to said frame parallel to a main axis and equally spaced therearound, a die shaft eccentrically journalled on each said die holder on an axis generally parallel to said main axis, a thread-rolling die with a thread formed thereon fixed to each die shaft for cooperation with a workpiece coaxial with said main axis, said thread-rolling dies being symmetrically spaced around the periphery of said Workpiece, means to drive each said die shaft at the same rotational speed including a main spiral gear journalled on said frame, a driven spiral gear longitudinally movable relative to said main spiral gear and meshing therewith, means connecting said driven spiral gear to rotate one of said dies, radial dept-h means to control partial rotation of said die holders to control eccentric movement of said thread-rolling dies to control radial depth of threadrolling on said workpiece, a control cam driven from said drive means and journalled on said frame, a cam follower cooperating with said control cam, means connectin-g said cam follower to longitudinally move said driven spiral gear to partially rotate the respective one of said thread-rolling dies relative to the others, means to adjust the relative timing of the starts of the threads on the respective dies to be synchronized at the beginning of each cycle of operation, and one revolution of said control cam establishing one cycle of operation to form a threaded workpiece from a 'blank, whereby during one cycle said control cam longitudinally moves said driven spiral gear and hence changes the timing of the start of the thread of the respective thread-rolling die relative to the others first in one arcuate direction from synchronized position and then return in the opposite arcuate direction to said synchronized position to perform a finishing operation on one side of the thread formed during one cycle of operation.

9. A thread-rolling machine comprising in combination, a frame, a main spiral gear journalled on said frame, means to drive said spiral gear, a plurality of driven spiral gears rotatively mounted and longitudinally movable relative to said main spiral gear and meshing with said main spiral gear, a die holder for each driven spiral gear and journalled on said frame, a die shaft eccentrically journalled on each said die holder on an axis generally parallel to said main spiral gear and connected to be driven therefrom through the respective driven spiral gear, a thread-rolling die with a thread formed thereon fixed on each die shaft for cooperation with a workpiece coaxial with said main shaft, said thread-rolling dies being symmetrically spaced around the periphery of said workpiece, radial depth means connected to each said die holder to control partial arcuate movement thereof to control movement of said thread-rolling dies to control radial depth of thread-rolling on said workpiece, a control cam journalled on said frame, a cam follower cooperating with said control cam, means to drive said control cam in accordance with rotation of said main spiral gear, means connecting said cam follower to longitudinally move one of said driven spiral gears to partially rotate the respective one of said thread-rolling dies, means to adjust the relative timing of the starts of the threads on the respective dies to be synchronized at the beginning of each cycle of operation, and one revolution of said control cam establishing one cycle of operation to form a threaded workpiece from a blank, whereby during one cycle said control cam longitudinally moves said one of said driven spiral gears and hence changes the timing of start of the thread of the respective thread-rolling die relative to the others first in one arcuate direction from synchronized position and then return in the opposite arcuate direction to said synchronized position to perform a finishing operation on one side of the thread formed during one cycle of operation.

10. A thread-rolling machine comprising in combination, a frame, a main shaft journalled on said frame, means to drive said shaft, a spiral gear fixed on said shaft, a plurality of drive shafts journalled in said frame parallel to said main shaft and equally spaced therearound, a driven spiral gear splined rotatively connected and longitudinally movable relative to each said drive shaft meshing with said main spiral gear, a die holder for each drive shaft journalled on said frame, a die shaft eccentrically journalled on each said die holder on an axis generally parallel to each said drive shaft and connected to be driven therefrom, a thread-rolling die with a thread thereon fixed on each die shaft for cooperation with a workpiece coaxial with said main shaft, said thread-rolling dies being symmetrically spaced around the periphery of said workpiece, means connected to each said die holder to control partial rotation thereof to control eccentric movement of said thread-rolling dies to control radial depth of thread-rolling on said workpiece, a control cam journalled on said frame, a cam follower cooperating with said control cam, means connecting said cam follower to longitudinally move one of said driven spiral gears to partially rotate the respective one of said thread-rolling dies, means to adjust the relative timing of the starts of the threads on the respective dies to 'be synchronized near the beginning of each cycle of operation, and means to drive said control cam in accordance with rotation of said main shaft to longitudinally move said one of said driven spiral gears and hence change the timing of the start of the thread of the respective thread-rolling die relative to the others first in one arcuate direction from synchronized position and then return in the opposite arcuate direction to said synchronized position to perform a finishing operation on one side of the thread formed during one cycle of thread forming operation.

11. A thread-rolling machine comprising in combination, a frame, a main shaft journalled on said frame, means to drive said shaft, a spiral gear fixed on said shaft, a plurality of drive shafts journalled in said frame parallel to said main shaft and equally spaced therearound, a driven spiral gear rotatively connected and longitudinally movable relative to each said drive shaft meshing with said main spiral gear, a die holder for each drive shaft journalled on said frame, a die shaft eccentrically journalled on each said die holder on an axis generally parallel to each said drive shaft and connected to be driven therefrom, a thread-rolling die with a thread formed thereon fixed on each die shaft for cooperation with a workpiece coaxial with said main shaft, said thread-rolling dies being symmetrically spaced around the periphery of said workpiece, a radial depth cam driven in accordance with rotation of said main shaft, means connecting said cam to each said die holder to control partial rotation thereof to control eccentric movement of said thread-rolling dies to control radial depth of thread-rolling on said workpiece, a control cam journalled on said frame, a cam follower cooperating with said control cam, means connecting said cam follower to longitudinally move one of said driven spiral gears to partially rotate the respective one of said thread-rolling dies, one revolution of said radial depth cam establishing one cycle of operation to form a threaded workpiece from a blank, means to adjust the relative timing of the starts of the threads on the respective dies to be synchronized at the beginning of each cycle of operation, and means to drive said control cam at the same speed as said radial depth cam, whereby during one cycle said control cam longitudinally moves said one of said driven spiral gears and hence changes the timing of the start of the thread of the respective thread-rolling die relative to the others first in one arcuate direction from synchronized position and then return in the opposite arcuate direction to said synchronized position to perform a finishing operation on one side of the thread formed during one cycle of operation of said radial depth cam.

12. A thread-rolling machine comprising in combination, a frame, a main shaft journalled on said frame, means to drive said shaft, a spiral gear fixed on said shaft, a plurality of drive shafts journalled in said frame parallel to said main shaft and equally spaced therearound, a driven spiral gear rotatively connected and longitudinally movable relative to each said drive shaft meshing with said main spiral gear, a die holder coaxially journalled around each said drive shaft and journalled on said frame, a die shaft eccentrically journalled on each said die holder on an axis generally parallel to each said drive shaft and geared to be driven therefrom, a thread-rolling die with a thread formed thereon fixed on each die shaft for cooperation with a workpiece coaxial with said main shaft, said thread-rolling dies being symmetrically spaced around the periphery of said workpiece, means connected to each said die holder to control partial rotation thereof to control eccentric movement of said thread rolling dies to control radial depth of thread-rolling on said workpiece, a cam journalled on said frame, a cam follower cooperating with said cam, means connecting said cam follower to longitudinally move one of said driven spiral gears to partially rotate the respective one of said thread rolling dies, means to adjust the relative timing of the starts of the threads on the respective dies to be synchronized at the beginning of each cycle of operation, and means to drive said cam in accordance with rotation of said main shaft, whereby during one thread forming cycle said cam longitudinally moves said one of said driven spiral gears and hence changes the timing of the start of the thread of the respective thread-rolling die relative to the others first in one arcuate direction from synchronized position and then return in the opposite arcuate direction to said synchronized position to perform a finishing operation on one side of the thread formed on a workpiece during one cycle of operation.

13. A thread-rolling machine comprising in combination, a frame, a main shaft journalled on said frame, means to drive said shaft, a spiral gear fixed on said shaft, a plurality of drive shafts journalled in said frame parallel to said main shaft and equally spaced therearound, a driven spiral gear splined to each said drive shaft meshing with said main spiral gear, a die holder coaxially journalled around each said drive shaft and journalled on said frame, a die shaft eccentrically journalled on each said die holder on an axis generally parallel to each said drive shaft and geared to be driven therefrom, a threadrolling die having a thread formed thereon fixed on each die shaft for cooperation with a workpiece coaxial with said main shaft, said thread-rolling dies being symmetrically spaced around the periphery of said workpiece, a radial depth cam driven in accordance with rotation of said main drive shaft, means connecting said cam to each said die holder to control partial rotation thereof to control eccentric movement of said thread-rolling dies to control radial depth of thread-rolling on said workpiece, a face cam journalled on said frame, a cam follower cooperating with said face cam, means connecting said cam follower to longitudinally move one of said driven spiral gears, one revolution of said radial depth cam establishing one cycle of operation to form a threaded workpiece from a blank, means to adjust the relative timing of the starts of the threads on the respective dies to be synchronized at the beginning of each cycle of operation, and means to drive said face cam at the same speed as said radial depth cam, whereby during one cycle aid face cam longitudinally moves said one of said driven spiral gears and hence changes the timing of the start of the thread of the respective thread-rolling die relative to the others first in one arcuate direction from synchronzed position and then return in the opposite arcuate direction to said synchronized position to perform a finishing operation on one side of the thread formed during one cycle of operation of said radial depth cam.

14. A thread-rolling machine comprising in combination, a frame, a main shaft journalled on said frame, means to drive said shaft, a spiral gear fixed on said shaft, a plurality of drive shafts journalled in said frame parallel to said main shaft and equally spaced therearound, a driven spiral gear splined to each said drive shaft meshing with said main spiral gear, a die holder coaxially mounted around each said drive shaft and journalled on said frame, a die shaft eccentrically journalled on each said die holdor on an axis parallel to each said drive shaft and geared to be driven therefrom, a thread-rolling die with a thread formed thereon fixed on each die shaft for cooperation with a workpiece coaxial with said main shaft, said thread-rolling dies being symmetrically spaced around the periphery of said workpiece, a gear on each said die holder and all of the same diameter, a control gear meshing with said gear on each said die holder, a radial depth cam driven in accordance With rotation of said main drive shaft and connected to said control gear to control partial rotation thereof to control eccentric movement of said thread-rolling dies to control radial depth of thread-rolling on said workpiece, an adjusting block connected to longitudinally move at least one of said driven spiral gears, a cam follower, lock screw mean rotatively adjustable and interconnecting said adjusting block and said cam follower, an eccentric path face cam journalled on said frame and cooperating with said cam follower, gearing interconnecting said face cam and said main shaft, said gearing establishing one revolution of said face cam for each revolution of said radial depth cam to effect one cycle of operation to form a threaded workpiece from a blank, whereby one revolution of said face cam longitudinally moves said one of said driven spiral gear and hence changes the timing of the start of the thread of the respective one of said thread-rolling dies relative to the others, first in one arcuate direction from synchronized position and then return in the opposite arcuate direction to said synchronized position to perform a finishing operation on one side of the formed thread during one cycle of operation of said radial depth cam.

15. A thread-rolling machine comprising in combination, a frame, a main shaft journalled on said frame, means to drive said shaft, a spiral gear fixed on said shaft, a plurality of drive shafts journalled in said frame parallel to said main shaft and equally spaced therearound, a driven spiral gear splined to each said drive shaft meshing with said main spiral gear, a die holder coaxially mounted around each said drive shaft and journalled on said frame, a die shaft eccentrically journalled on each said die holder on an axis parallel to each said drive shaft and geared to be driven therefrom a thread-rolling die with a thread formed thereon fixed on each die shaft for cooperation with a workpiece coaxial with said main shaft, said thread-rolling dies being symmetrically spaced around the periphery of said workpiece, a gear on each said die holder and all of the same diameter, an internal toothed ring gear meshing with said gear on each said die holder, a radial depth cam driven by gearing in accordance with rotation of said main drive shaft and connected to said ring gear to control partial rotation thereof to control eccentric movement of said thread-rolling dies to control radial depth of thread-rolling on said workpiece, an adjusting block connected to longitudinally move each of at least two of said driven spiral gears, cam follower means, lock screw means rotatively adjustable and interconnecting each of said adjusting blocks and said cam follower means, an eccentric path face cam means journalled on said frame and cooperating with said cam follower means, gearing including change gears interconnecting said face cam means and said main shaft, said gearing establishing one revolution of said face cam means for each revolution of said radial depth cam to effect one cycle of operation to form a threaded workpiece from a blank whereby one revolution of said face cam means longitudinally moves said at least two of said driven spiral gears and hence rotates the respective driven spiral gears and changes the timing of the start of the thread of the respective thread-rolling dies relative to the others, first in opposite arcuate directions from synchronized position and then in return arcuate directions to said synchronized position to perform a finishing operation on both sides of the formed thread during one cycle of operation of said radial depth cam.

16, A thread-rolling machine comprising in combination, a frame, a main shaft journalled on said frame, means to drive said shaft, a spiral gear fixed on said shaft, first, second and third drive shafts journalled in said frame parallel to said main shaft and equally spaced therearound, a driven spiral gear splined to each said drive shaft and meshing with said main spiral gear, first, second and third die holders journalled on said frame coaxial with said first, second and third drive shafts, respectively, a die shaft eccentrically journalled on each said die holder on an axis parallel to each said drive shaft and geared to be driven therefrom, a thread-rolling die with a thread formed thereon fixed on each die shaft for cooperation with a workpiece coaxial with said main shaft, said three thread-rolling dies being symmetrically spaced around the periphery of said workpiece, gears of the same diameter on said die holders, an internal toothed ring gear meshing with said gear on each said die holder, a radial depth cam driven in accordance with rotation of said main drive shaft and connected to said ring gear to control partial rotation thereof to control eccentric movement of said thread-rolling dies to control radial depth of thread-rolling on said workpiece, an adjusting block longitudinally fixed to at least one of said driven spiral gears, a cam follower, lock screw means rotatively adjustable and interconnecting said adjusting block and said cam follower, an eccentric path face cam journalled on said frame and cooperating with said cam follower, gearing including change gears interconnecting said face cam and said main shaft, and said gearing establishing one revolution of said face cam for each revolution of said radial depth cam to effect one cycle of operation to form a threaded workpiece from a blank whereby one revolution of said face cam longitudinally moves said one of said driven spiral gears and hence rotates the respective driven spiral gear and changes the timing of the start of the thread of the respective one of said thread-rolling dies relative to the other two, first in one arcuate direction from synchronized position and then return in the opposite arcuate direction to said synchronized position to perform a finishing operation on one side of the formed thread during one cycle of operation of said radial depth cam.

References Cited by the Examiner UNITED STATES PATENTS 855,658 6/1907 OBrien 72107 957,440 5/1910 OBrien 72108 964,272 7/ 1910 Kaiserrnan 72107 1,068,236 7/1913 Girlot 72107 2,624,218 1/1953 Flanders et a1 72104 3,024,677 3/1962 Greiman et al 72108 CHARLES W. LANHAM, Primary Examiner.

H. D. HOINKES, Assistant Examiner. 

1. A FORM-ROLLING MACHINE COMPRISING IN COMBINATION, A FRAME HAVING AN AXIS, A PLURALITY OF FORM-ROLLING DIES JOURNALLED RELATIVE TO SAID FRAME GENERALLY PARALLEL TO A MAIN AXIS AND EQUALLY SPACED THEREAROUND FOR COOPERATION WITH A WORKPIECE POSITIONABLE ON SAID AXIS, MEANS TO RELATIVELY ROTATE ANY SAID WORKPIECE AND SAID DIES FOR ROLLING A FORM ON SAID WORKPIECE, RADIAL DEPTH MEANS TO CONTROL RADIAL MOVEMENT OF SAID FORM-ROLLING DIES TO CONTROL RADIAL DEPTH OF FORM-ROLLING ON ANY WORKPIECE COAXIAL WITH SAID AXIS, A MEANS TO ADJUST THE RELATIVE TIMING OF THE FORM-ROLLING MEANS ON THE RESPECTIVE DIES TO BE SYNCHRONIZED AT THE END OF EACH CYCLE OF OPERATION, AND CONTROL MEANS CONNECTED TO MOVE ONE OF SAID DIES TO CHANGE THE EFFECTIVE TIMING THEREOF RELATIVE TO THE OTHERS FIRST IN ONE DIRECTION AND THEN RETURN IN THE OPPOSITE DIRECTION TO SAID SYNCHRONIZED POSITION TO PERFORM A FINISHING OPERATION ON THE FORM ROLLED ON THE WORKPIECE DURING THE THREAD-ROLLING OPERATION. 